This invention relates to apparatus for making disposable type diaper products and, more particularly, diaper products (such as diapers per se and training pants) wherein there is a contoured leg elastic. A representative prior art patent is U.S. Pat. No. 4,801,345.
The principal object of this invention is to create elastic gathers around the leg openings in disposable products such as the above-mentioned infant diapers and training pants Two problems are involved which the invention has solved.
A first problem lies in the inability to hold the elastic in the desired contour. Once the elastic strand or strands are laid down onto the adhesive-equipped web, the cross machine forces tend to roll or slide the elastic, reducing the amplitude of the profile. The amount of change is a function of adhesive "green tack", line speed and pressing means.
A second problem lies in the fact that elastic profiles may differ significantly from the profile program for the guide means for the elastic. This is due to the length of elastic between the guide means and the adhesive-equipped web. Typically one to two inches of free elastic are involved. The guide would then need to travel the distance greater than the desired profile to account for the transverse distance lost in the free span of the elastic.
The first listed problem has been efficiently solved through the provision special guide means in combination with a pair of nip rolls and the second problem relating to maintaining the desired profile has been solved by trapping the elastic strands between two webs, typically one of nonwoven and one of polyethylene.
Japanese Applications 4028-363-A and 4028-364-A show introducing contoured leg elastic strands between two plies of the diaper, U.S. Pat. No. 5,147,487 which show a single web plus contoured elastic strands passing between a pair of rollers and PCT WO 89/09550 which shows contoured strands applied to a web.
According to the instant invention, the two webs, at least one of which has adhesive, are passed along with the elastic strands into a two-roll nip and subsequently travel in partial wrapping engagement with one of the rolls. Thus, the outer web tension is converted to pressure so that the strand profile is preserved by giving the glue time to set so as to maintain the width of the webs.